Two stroke internal combustion engines have the potential to be more energy efficient than four-stroke engines because each downward stroke is a power stroke. Two stroke designs have not been fully fuel efficient, however, because they have not had effective fuel and air intake methods nor effective means of scavenging exhaust gases. Four stroke engines have the disadvantage of requiring energy to operate the extra two strokes, their camshafts, and their reciprocating valves. Further, neither current two stroke nor four stroke engines have ideal fuel vaporization processes.
The invention described herein relates to an improvement to the energy efficiency of the internal combustion engine using the two stroke concept and incorporating a more energy efficient method of introducing air into the cylinders and scavenging than that employed in previous designs. These functions can be accomplished with this new design as effectively as with the four stroke design, and this new design avoids the energy losses due to the two additional strokes of the four stroke engine. The invention also obviates the need for a camshaft and reciprocating valves, thus saving the energy required for their operation, and thereby increasing energy efficiency.
The energy efficiency of the internal combustion engine is improved with a unique two stroke design which uses the air pressure from a rotary compressor (centrifugal, axial-flow, etc.) to open the two air intake valves located in the cylinder head, and to force air into the cylinders for combustion and scavenging. The air is introduced substantially parallel to the inside bottom surface of the cylinder head, and the air is constrained by the cylinder walls and head configuration to swirl and rotate rapidly, thus flowing over the top of the combustion gases as the air enters the cylinder rather than mixing with the combustion gases. Scavenging is accomplished when the downwardly moving piston uncovers exhaust ports in the cylinder wall. The pressure from the expanding combustion gases in combination with the pressure of the air entering the cylinder from the rotary compressor causes the combustion gases to exit the cylinder through the exposed exhaust ports. The intake air which fills the cylinder during scavenging is then compressed for the next power stroke as the piston moves upward.
A fuel injector is located in the cylinder head and introduces fuel into the swirling air in the combustion chamber as the piston nears the top of its compression stroke. A spark plug is located in a position near the injector and ignites the fuel while the fuel-air mixture is rich. This arrangement permits the injection of a minimum quantity of fuel in order to achieve a maximum fuel economy. The air continues to swirl in the cylinder during ignition, burning, and scavenging, thereby further contributing to the efficiency of the engine.
Energy efficiency is enhanced by: 1) minimizing the energy expended to introduce air into the cylinders; 2) minimizing the quantity of fuel required for each power stroke through use of a more effective vaporization technique; 3) igniting a rich fuel-air mixture followed by burning as the air continues to swirl in the combustion chamber; 4) producing more rapid and complete burning; and 5) minimizing the energy expended to scavenge the exhaust gases from the cylinders. Further improvements in efficiency are accomplished by the elimination of reciprocating valves and the camshaft required by conventional four-stroke engines, and by eliminating the frictional losses inherent in the additional two strokes of four-stroke engines.
Because more complete burning of fuel is achieved due to the swirling of the air in the cylinder during burning, and because air from the rotary compressor contacts the combustion gases as the scavenging process occurs, exhaust pollutants from the engine are minimized. Consequently, there is less need for power-consuming anti-pollution devices like those currently employed on many four-stroke engines. Also, the exhaust system is configured to reduce exhaust sound, thereby reducing or eliminating the need for a muffler, and thereby avoiding back pressure from a muffler.